1. Field
Exemplary embodiments relate to a frequency measuring circuit, and particularly to a frequency measuring circuit that measures frequency of an input clock signal and outputs information for the frequency of the clock signal, and a semiconductor device having the same.
2. Description of Related Art
Internal circuits of a semiconductor device operate differently from each other. Accordingly, clock signals input to a semiconductor device may have various frequencies. For example, when the frequency of the clock signal input to the semiconductor device is high, the semiconductor device may be designed to supply a large current to an input/output driver to raise driving capability. Further, when the frequency of the clock signal input to the semiconductor device is low, the semiconductor device may be designed to supply a relatively small current to the input/output driver. Further, in the case of a semiconductor memory device, the circuit may be designed to have a large latency when the frequency of the clock signal input to the semiconductor device is high, and have a small latency when the frequency of the clock signal input to the semiconductor device is low. Further, a delay-locked-loop (DLL) may be used to generate the internal clock signal that is synchronized with a clock signal supplied from the exterior. The delay circuit having a short delay time may be used to synchronize the internal clock signal with the external clock signal when the frequency of the clock signal input from the exterior is high, but the delay circuit having a long delay time is required when the frequency of the clock signal input from the exterior is low.
Therefore, information related to the frequency of the clock signal input from the exterior is required to optimize operation of the semiconductor device.